1. Field of the Invention
The present invention relates to a reception device, an antenna, and a junction cable and can be used for a mobile-phone system that can receive a digital-radio broadcast, etc. According to the present invention, one of sides of a path provided to transmit a high-frequency signal is used as an antenna ready for a specified frequency band, the side extending from a main-body device to a predetermined point, and the other side of the path is assigned as a path provided to transmit an audio signal, etc., so that an antenna achieved to be mechanically strong, finely designed, and high performance by using a simpler configuration than in the past, a reception device using the antenna, and a junction cable that can be used for the antenna are proposed.
2. Description of the Related Art
Heretofore, many ideas relating to an antenna have been embodied in mobile reception devices. Namely, it is desirable that antennas used for mobile reception devices or the like do not compromise the design of the mobile reception devices, reduce effects produced on the human body, resist damages caused by noises emitted from electronic gear, etc.
In the past, regarding the design problem, the antennas were included in the reception devices, so as not to comprise the design of the reception devices. However, since the antennas are increased in size in an ultra-high-frequency (UHF) band and a very-high-frequency (VHF), it was difficult to include the antennas in the reception devices. In the past, therefore, the reception devices used in the UHF band and the VHF band were usually provided with rod antennas. However, when the rod antenna is provided in the reception device, the configuration of the reception device becomes complicated. Further, the rod antenna juts out the reception device so that the design of the reception device is compromised, for example.
Accordingly, various types of methods of using an earphone cable as the antenna have been proposed in recent years. However, when the earphone cable is simply used as the antenna, the earphone cable is brought into contact with the human body, as shown in FIG. 42. Further, since various parts of the earphone cable are brought in contact with the human body, it has been difficult to make full use of functions of the antenna.
Therefore, various ideas of making it difficult for a part of the earphone cable to function as the antenna, the parts being brought into contact with the human body, have been proposed. For example, according to Japanese Unexamined Patent Application Publication No. 2005-64742, Japanese Unexamined Patent Application Publication No. 2006-25392, and Japanese Patent No. 3851339, a part of the earphone cable is formed as a coaxial cable, the part being provided on the reception-device side.
According to the above-described methods, however, a high-frequency-elimination element which eliminates the entry of a high-frequency signal to a specified region should be provided in a connection part where a non-antenna part and an antenna part of the earphone cable are connected to each other. Subsequently, the configuration of the connection part becomes more complicated and the mechanical strength of the earphone cable deteriorates at the connection part. Further, the design of the reception device is limited. Still further, when the high-frequency-elimination element is provided in the connection part, a direct-current resistance occurring in an audio-signal-transmission path is increased, and sound-output characteristics of the earphone cable are deteriorated. Therefore, the performance of the earphone cable using the above-described methods is not sufficient in practice.